1. Field of the Invention
The invention relates to a pressure sensitive adhesive composition suitable for application to human or animal skin, to a method for preparing such adhesives and the use of such adhesive for the preparation of a wound dressing or an adhesive wafer for an ostomy appliance or the use of the adhesive agent for securing of and sealing around ostomy bandages, for securing wound dressings, for securing of devices for collecting urine, wound-drainage bandages, orthoses and prostheses and for protecting skin areas and parts of the body against pressure, impacts and friction. Furthermore, the invention relates to ostomy appliances and wound dressings comprising such adhesive composition.
2. Description of the Related Art
Various skin adhesive agents are used today for the above mentioned purposes.
A very widespread embodiment of skin adhesive agents comprises a self-adhesive elastomeric matrix, in which water-absorbing, swelling particles, the so-called hydrocolloids, are dispersed.
Adhesive compositions comprising hydrocolloids have been known for many years. U.S. Pat. No. 3,339,549 discloses a blend of a rubbery elastomer such as polyisobutylene and one or more water soluble or water swellable hydrocolloids such as a powdery mixture of pectin, gelatine and carboxymethylcellulose. The adhesive mass has a water-insoluble film applied to one surface. A composition of this type is available commercially from E. R. Squibb & Sons Inc. under the trademark "Stomahesive" and is used as a skin barrier around stomas to prevent skin breakdown by the corrosive fluids discharged by the stoma.
In adhesive compositions of this type, the polyisobutylene is responsible for provision of the adhesive properties and the dispersed hydrocolloid powders absorb fluid and render the adhesive agent capable of also adhering to moist skin (wet tack). These compositions are also gaining increasing acceptance as wound dressings for dermal ulcers, burns and other exuding wounds.
One major problem which has been encountered with conventional adhesive compositions comprising hydrocolloids is their susceptibility to breakdown upon exposure to body fluids. When the compositions are used as skin barriers, e.g., around stomas, absorption of fluid is desirable, but excessive swelling causes the composition to lose its integrity opening for leaks and the barrier must be replaced more often than is desirable from a skin protection point of view, and very often, a residue remains on the skin, which in many cases is difficulty to remove.
Another major problem for conventional adhesive compositions comprising hydrocolloids is their limited capability in adhering to moist body surfaces. There is particularly a need for an improved adhesive composition having an enhanced adhesion to moist skin in the management of ostomy patients, as it is often difficult to keep the skin around stomas completely dry during replacement of an ostomy appliance.
When bandaging wounds, contact with the wound exudate will in a similar way effect a disintegration of the adhesive agent which means that when the bandage is changed remnants will be left in the wound, which remnants may affect the wound-healing process. Besides during use, leakage may arise which partly means reduced time of use, and partly may increase the risk of contaminating the wound with bacteria or other microorganisms.
Adhesive agents are also used for securing devices, such as uridomas, for collecting the urine from incontinent men. Disintegration of the adhesive agent due to contact with urine will again mean a risk of leakage and a reduction of the time of use.
Adhesive agents are also employed for securing orthoses and prostheses (e.g., breast prostheses) and for protection of skin areas or parts of the body against pressure, impact and friction. In these cases it is primarily the secretion of sweat which may cause swelling and disintegration of the adhesive agent. When removing the adhesive agent remnants will be left on the skin, involving the inconveniences earlier mentioned.
A number of attempts have been made to improve the integrity of adhesive compositions.
As a method for improving the adhesive integrity, the use of hydrocolloids has been described which, in themselves, are cross-linked (e.g., cross-linked carboxymethylcellulose (CMC), cross-linked dextrane and other water-absorbing, but insoluble hydrocolloids). They will not dissolve due to the cross-linked structure. During the swelling process the individual particles will, therefore, obtain a gel-like structure, but no coherent gel could be formed since the macromolecules of the cross-linked hydrocolloids are locked in the gel network constituted by the individual particles. Due to the lack of a coherent gel, the cross-linked hydrocolloids will be leached out and suspended in the body fluids and the effect on the integrity of the swelled adhesive, therefore, is limited.
Alternatively, as described below, it has been tried to increase the integrity of the swelled adhesive agent by increasing the cohesion of the elastomeric phase. The elastomeric phase, therefore, will not so easily be split by the expanding hydrocolloids during the swelling process. This process, however, has a number of drawbacks:
The rate of water absorption and thus the "wet tack" of the adhesive agent will be reduced. PA1 By strengthening the cohesion the elastomeric matrix will have stronger elastic properties. When the hydrocolloids absorb water and swell, this will enhance an increase in the dimensions of the adhesive agent. Due to the elastic properties of the matrix, the tensions occurring in the adhesive agent cannot be relaxed by plastic deformation. Instead pleats may occur in the adhesive agent around the swelled area. In these pleats the adhesive agent will loose contact with the skin exposed to the body fluids, and a risk of leakage arises.
U.S. Pat. Nos. 4,192,785 and 4,551,490 describe incorporating into an adhesive composition a cohesive strengthening agent such as a natural or synthetic fibrous material, finely divided cellulose, cross-linked dextran, cross-linked carboxymethylcellulose or a starch-acrylonitrile graft copolymer. The cohesive strengthening agent is stated to control the rate of hydration of the composition thereby increasing the resistance against breakdown by body fluids.
U.S. Pat. No. 4,477,325 describes incorporation of a mixture of a copolymer resin of ethylene and vinyl acetate (EVA) into the adhesive composition. After mixing and moulding, the composition is subjected to ionising radiation to form a cross-linked polymer network of the EVA or comprising EVA and another cross-linked resin. The cross-linked matrix is said to provide a controlled swelling.
U.S. Pat. No. 4,496,357 describes the incorporation of fumed silica into adhesive compositions to control swelling.
EP No. 0 122 344 B1 describes incorporation of one or more natural or synthetic polymers capable of developing elastomeric properties when hydrated, such as gluten and long chain polymers of methyl vinyl ether/maleic acid, into the adhesive composition. The adhesive composition is stated to be resistant to erosion by moisture and body fluids.
EP Patent No. 0 340 945 B1 describes incorporation of some polycationic hydrocolloid particles into a hydrocolloid composition. The mixture of polycationic, polyanionic and neutral hydrocolloids is stated to provide increased integrity without a concomitant decrease in absorbing capacity.
In existing adhesive agents the surface of the adhesive is consisting of the self-adhesive elastomeric matrix while the hydrocolloids are located embedded beneath the surface in the elastomeric matrix. In order to be absorbed, the water thus needs to penetrate through the elastomeric matrix before reaching the water absorbing hydrocolloids. This retards the water-absorption and causes that the adhesive agent does not have an immediately adhesion to wet surfaces (wet tack).
Thus, there is still a need for an adhesive agent showing a very rapid water absorption and retention in order to improve the wet tack.
Skin problems associated with an ostomy are different from skin problems generally associated with adhesives for skin (dressings or plasters) as the adhesives of ostomy appliances are placed permanently at the same site during long periods of time (cronical irritation) whereas other adhesives for skin are normally only placed at the same site for a short period of time.
European Patent publication No. EP 0 017 401 A1 discloses articles of manufacture having adhesive properties useful for, for example, protective plasters or dressings or as rings, washers or the like in surgical appliances such as ostomy appliances comprising a plastics matrix comprising the product resulting from heating together one or more polyhydric alcohols and gelatine and/or naturally occurring high molecular weight polysaccharide gum and/or a resin which is a copolymer and a vinyl ether and an organic acid anhydride and/or its corresponding free acid. Polyvinylpyrrolidone resin may be added as a tack modifier.
European Patent publication No. EP 0 343 807 A2 discloses absorptive adhesive dressing with controlled hydration containing about 30-65% polyisobutylene, 10-30% polyvinylpyrrolidone, 2-20% modified starch, 2-20% pectin, 0.1-10% acrylic polymer and 0-1% fibre. The dressing disclosed in EP 0 343 807 A2 is a nonocclusive dressing providing a controlled water evaporation from the wound area.
European Patent publication No. EP 0 063 898 discloses a microporous tape comprising a porous backing layer and a microporous adhesive layer including a rubbery elastomer such as polyisobutylene, one or more water swellable hydrocolloids and other optional substances. A copolymer of polyvinylpyrrolidone and vinylacetate may be used as a tackifier.
European Patent publication No. EP 0 591 898 A1 discloses adhesive compositions and wound dressings comprising an adhesive composition comprising a blend of a hydrophobic unsaturated aliphatic homopolymer, a compatible tackifier and at least one hydrocolloid adsorbent which composition has been exposed to a dose of ionising radiation which chemically cross-links the unsaturated aliphatic homopolymer component.
It has surprisingly been found that the use of an adhesive comprising a conjugated diene polymer and a polyvinyl pyrrolidone polymer or a polyvinyl pyrrolidone vinylacetate copolymer improves the rate of absorption of water and improves the tack of an adhesive agent on wet skin and the cohesion of the adhesive agent and also improves the performance towards the action of aggressive exudates or excretions from a body without having to rely on the addition of other ingredients. Furthermore, it has surprisingly been found that the presence of an acrylic elastomer as a complementary binder is not necessary and that it is not necessary to have to rely on a chemical cross-linking and addition of a tackifier in order to obtain an adhesive composition showing satisfactory properties, physical cross-linking has been found to be sufficient.